The present invention relates in general to tools for marking biological tissue during surgical procedures, and, more specifically, to improved accuracy and integrity of tissue marking by drying of the biological tissue.
In preparation for cutting, suturing, or other surgical steps, a surgeon may first identify and mark locations on tissue to properly orient and locate targeted tissue. For example, in coronary artery bypass grafting (CABG), a blood vessel is “harvested” (i.e., removed) from its natural location in a patient's body and reattached elsewhere to create a blood flow around a blockage. After a vessel is removed from the patient's body, it must be prepared for use as a bypass graft. Preparation includes ligating (i.e., closing off) each branch stub, injecting a solution into the vein under pressure to test for leaks, and otherwise inspecting the condition of the blood vessel. After preparation, the vessel can be surgically anastomosed to create the bypass.
It has become common for vessel preparation to include application of a longitudinal guide line along the outer wall of the graft comprised of a methylene blue dye. The line is intended to help in laying out the graft by showing if the graft becomes twisted, which could cause kinking and poor blood flow through the bypass. To apply the guide line, a surgeon or physician's assistant has manually marked the vessel using a felt tip pen filled with the methylene blue dye. The vessel is kept moist with heparinized saline to preserve it while outside the body. The moisture, however, can cause the dye to “run” or diffuse so that the lines blur. This makes it difficult to achieve the pin-point accuracy desired for many procedures.
Other examples of wet tissue marking include 1) marking the internal surface of a live human aortic valve (which are wet from saline and blood) during repair of the valve to indicate suture positions, 2) internally marking cadavers and living animal tissues for various procedures and for marking dissected specimens, and 3) marking the outer surface of wet human eyes.
In addition to marking with a dye such as methylene blue, other means of marking tissue such as laser scoring, tattooing, heat burning, and cold burning can also be adversely affected by moisture on the tissue surface to be marked.